Weather Facts: Air masses and their sources | badz.info
We can then make combinations of the above to describe various types of air shifts in wind direction; Pressure changes; Clouds and precipitation patterns. Six basic types of air masses affect the weather of the British Isles. They can bring anything from tropical warm and humid days to arctic cold depending on the. The complex relationships between fronts cause different types of wind and Prevailing winds are winds that blow from a single direction over a . Some equatorial air masses return to the doldrums as trade winds, while.
What causes Air Pressure? Air pressure depends on the density of the air, or how close together its molecules are. You know that a hard rubber ball is more dense than a Styrofoam ball and that ice cream is more dense than whipped cream.
Wind & Air Pressure
Air lower in the atmosphere is more dense than air above, so air pressure down low is greater than air pressure higher up. Remember those acrobats; there's a lot more pressure on the one on bottom than on the one on top. Temperature also makes changes in air pressure. In cold air, the molecules are more closely packed together than in warm air, so cold air is more dense than warm air.
Rising and Sinking Air Since warm air is less dense and creates less air pressure, it will rise; cold air is denser and creates greater air pressure, and so it will sink. When warm air rises, cooler air will often move in to replace it, so wind often moves from areas where it's colder to areas where it's warmer.
The greater the difference between the high and low pressure or the shorter the distance between the high and low pressure areas, the faster the wind will blow.
Air mass types - Met Office
Wind also blows faster if there's nothing in its way, so winds are usually stronger over oceans or flat ground. Meteorologists can forecast the speed and direction of wind by measuring air pressure with a barometer. Wind Direction Although wind blows from areas of high pressure to areas of low pressure, it doesn't blow in a straight line. That's because the earth is rotating.
Air Masses and Fronts
In the northern hemisphere, the spin of the earth causes winds to curve to the right to the left in the southern hemisphere. When the wind is from the prevailing direction then the weather is generally typical.
When the wind shifts away from the prevailing direction then it often indicates atypical or changing weather. For your forecast location, note what type of environment is located in every direction from the location.
Take Dallas for example, toward the southeast is the moisture source of the Gulf of Mexico; toward the east is the typically warm and humid southeast; toward the north are the plains which can bring in cooler air in the cool season; toward the west and southwest is a very dry high elevation climate; toward the south is the transition between the coastal area and dry portions of Texas. A wind from the north in Dallas will tend to bring in cooler and drier air; a wind from the southwest will bring in very dry air; a wind from the southeast will bring in warm and humid air.
Just by noting the wind direction a forecaster gains an idea of what type of air mass is moving toward the forecast area. Wind direction changes often accompany changes in the weather.
The air flows cyclonically around low pressure systems. If the wind changes direction in a cyclonic fashion it often means a low pressure or front is influencing the forecast area.
A wind shifting from the south often means warmer air is approaching and a wind from the north often means cooler air is approaching.